1. FIELD OF THE INVENTION
The present invention relates to a saw tooth all-steel card clothing for a carding engine, which card clothing includes a foot section followed by a web section including the teeth.
2. DESCRIPTION OF THE PRIOR ART
In carding machines such card clothing in the form of saw-tooth wires are wound helically onto the main drum in a mutually closely abutting condition. This clothing cooperates with further card clothings located at the flat or the flats, respectively, of the carding engine and having a same or any other kind of design such to card fibres fed therebetween.
The customary dimensions of the saw tooth all-steel card clothing are set in accordance with the international standards ISO 5234, according to which the card clothing must have a total height of at least 2.0 millimeters. This total height is composed of the height of the foot section and the height of the web section of the saw-tooth wire, whereby the foot section can feature a height of 1.0-1.6-1.8 millimeters. The width of the foot is hereby in a range from 0.4 up to the commonly used maximal value of about 2.5 millimeters. For a carding of textile fibres consisting of natural or synthetic polymers by means of the common saw tooth all-steel card clothing, it is customary to use a card clothing on the main drums of the carding engines having a total height in the range of 2.0-3.2 millimeters, whereby the corresponding height of the foot is in the range from 1.2-1.4 millimeters.
It is generally known, that in operation of the carding machine when the main drum is rotating, not all fibres are driven by the centrifugal forces against the envelope of the main drum. Specifically, due to an irregular doffing from the main drum onto the doffer roller, a certain filling of the spaces between the respective web sections of adjacent sawtooth wires contacting each other by fibres occurs. Due to the continued feeding of further fibres to be carded, a condensing of fibres occurs now under the carding area between the teeth or needles, respectively, of the all-steel card clothing. Due to the fact that these fibres are pressed into the area of the all-steel card clothing where no carding happens, a considerable accumulation of fibres is formed in the mentioned dead spaces. Quite obviously the extent of this accumulation depends among other factors from the length of the fibres, from their crimp, from their surface structure and also from the thickness of the fibres. These fibres are now no longer caught by the tips of the teeth of the card clothing of the flats, i.e. they are generally displaced or removed, respectively, from the carding area. The doffing of the fibres by the doffing roller is also influenced and it is specifically possible, that an irregular transfer between main drum and doffer roller occurs, which produces obviously detrimental effects on the carded product.
Attempts have been made to overcome this drawback by a reducing of the volume present between the respective web sections by reducing the width of the foot. This led, however, to the drawback that the sawtooth wires tended to tilt laterally. When assembling the sawtooth wires on the jacket of the main drum, they must define together with the jacket an angle of 90.degree.. This leads to the fact that a reducing of the width of the foot is limited at least due to assembling reasons.
A further drawback of the known card clothing is that large air volumes are moved between and by the card clothing, which air volume can produce turbulences due to the high rotational speed (e.g. 300-600 rpm) of the main carding drum, which turbulences influence the effect of the carding detrimentally. Until now, attempts have been made to lead those masses of air away from the surface of the card clothing by means of slotted gratings and baffle plates outside of the carding area proper. Such measures have, however, only an extremely limited effect.